I have lost all my customers and all activities that I had on my app, is there anyway to retrieve without starting all over again

It's nice to have you in the Community, @smbplumbers-hotm. I’ll further assist you in sorting out this issue about your lost transactions in QuickBooks Online app.

First, you’ll want to ensure you’re logged in to the right account. Otherwise, you can verify this issue by logging into your QBO account in a browser.

In the meantime, let’s wipe the data from your QBO app to remove the cache histories. This way, it’ll help you sort out this issue with your transactions. Let me guide you on how:

For iOS app:

1. Go to Menu and tap Help & Feedback.
2. Tap Refresh Data.
3. Tap Refresh to confirm.
   
   

For Android app:

1. Go to Menu then tap More Options ⋮.
2. Tap Settings then Refresh Data.
3. Tap YES to confirm.
   
   

Once done, you might also need to uninstall, and reinstall the app just in case the issue persists. Here's an article as a guide: How to Download the QuickBooks Online Mobile App.

Furthermore, I'll share with you this article if you want to know more about the features you can access in the mobile app: Compare mobile app features.

Feel free to reach out if you have any further questions about managing your transactions in QBO. Have a good one!